Revert grisu commits.

test/cctest/test-dtoa.h

-static const int kBufferSize = 50;
-
-static double ComposeDouble(char* buffer, int sign, int length, int point) {
-  int k = point - length;
-  // Integrate exponent into buffer.
-  buffer[length] = 'e';
-  snprintf(&buffer[length+1], kBufferSize - length - 1, "%d", k);
-  double result;
-  sscanf(buffer, "%lf", &result);  // NOLINT
-  if (sign) {
-    result *= -1;
-  }
-  return result;
-}
-
-
-static bool IsCorrect(double v, char* buffer, int sign, int length, int point) {
-  return v == ComposeDouble(buffer, sign, length, point);
-}
-
-
-// The precision of long doubles is not enough to ensure the correct rounding.
-static bool IsRounded(double v, char* buffer, int sign, int length, int point) {
-  // We don't test when v is 0.
-  if (v == 0) return true;
-
-  // Simplify things by working with positive numbers.
-  if (v < 0) v = -v;
-  char correct_buffer[100];
-  snprintf(correct_buffer, sizeof(correct_buffer), "%.90e", v);
-  // Get rid of the '.'
-  correct_buffer[1] = correct_buffer[0];
-  char* correct_str = &correct_buffer[1];
-
-  int i = 0;
-  while (true) {
-    if (correct_str[i] == '\0' || correct_str[i] == 'e') {
-      // We should never need all digits.
-      return false;
-    }
-
-    if (buffer[i] == '\0' || buffer[i] == 'e') {
-      // Verify that the remaining correct digits are small enough.
-      if (correct_str[i] < '5') return true;
-      return false;  // For simplicity we assume that '5' is rounded up.
-    }
-
-    if (buffer[i] != correct_str[i]) {
-      if (buffer[i] < correct_str[i]) return false;
-      if (buffer[i] - correct_str[i] != 1) return false;
-      if (correct_str[i+1] < '5') return false;
-      return true;
-    }
-
-    // Both characters are equal
-    i++;
-  }
-}
-
-
-static bool IsShortest(double v,
-                       char* buffer,
-                       int sign,
-                       int length,
-                       int point) {
-  // Now test if a shorter version would still yield the same result.
-  // Not an exhaustive test, but better than nothing.
-
-  if (length == 1) return true;
-
-  char last_digit = buffer[length - 1];
-
-  if (buffer[length - 1] == '0') return false;
-
-  if (v == ComposeDouble(buffer, sign, length - 1, point)) {
-    return false;
-  }
-
-  bool result = true;
-  if (buffer[length-2] != '9') {
-    buffer[length - 2]++;
-    double changed_value = ComposeDouble(buffer, sign, length-1, point);
-    if (v == changed_value) {
-      printf("ROUNDED FAILED DEBUG: %s\n", buffer);
-      result = false;
-    }
-    buffer[length - 2]--;
-  }
-  buffer[length - 1] = last_digit;
-  return result;
-}